Metal—phenoxyalkanoic acid interactions. Part 14. The crystal and molecular structures of diaquabis(4-fluorophenoxyacetato)copper(II) bis(4-fluorophenoxyacetic acid)dihydrate and tetra-μ-(4-fluorophenoxyacetato-0,0′)-bis[(2-aminopyrimidine)copper(II)]

The crystal structures of two copper(II) complexes of 4-fluorophenoxyacetic acid (4-FPAH) have been determined by X-ray diffraction. [Cu(4-FPA)₂(H₂O)₂]·2(4-FPAH)·2H₂O (1) is triclinic, space group P1 with Z = 1 in a cell of dimensions a = 14.808(2), b = 9.832(2), c = 6.847(2) Å, α = 87.77(2), β = 98.41(2), γ = 112.33(2)° and was refined to a residual of 0.038 for 1697 ‘observed’ reflections. The coordination sphere in this complex is tetragonally distorted octahedral comprising two waters [CuO, 1.940(3) Å], two unidentate carboxylate oxygens [CuO, 1.942(2) Å] and two ether oxygens [CuO, 2.471(2) Å]. Two adducted [4-FPAH] acid molecules are linked to the un-coordinated oxygens of the acid ligands by hydrogen bonds [2.547(4) Å]. [Cu₂(4-FPA)₄(2-aminopyrimidine)₂] (2) is triclinic, space group P1 with Z = 1 in a cell of dimensions a = 12.688(2), b = 11.422(2), c = 7.951(1) Å, α = 78.74(1), β = 107.51(1), γ = 75.78(1)°, and was refined to a residual of 0.042 for 2683 ‘observed’ reflections. (2) is a centrosymmetric tetracarboxylate bridged dimer with four similar CuO (equatorial) distances [1.967–1.987 Å; 1.977(3) Å mean] and the axial position occupied by the hetero nitrogen of the 2-aminopyrimidine ligand [CuN, 2.176(3) Å]. The Cu---Cu separation is 2.710(1) Å. Crystal data are also presented which confirm the isostructurality of complex (2) with [Cu₂(phenoxyacetate)₄(2-aminopyrimidine)₂], the Co^II, Mg^II and Mn^II4-fluorophenoxyacetate complexes with their phenoxyacetic and 4-chlorophenoxyacetic acid analogues, and of Cd^II4-fluorophenoxyacetate with Cd^II and Zn^II phenoxyacetates.     

Solution and solid state behavior of Co2+, Ni2+ and Zn2+ tosylaminoacidate systems: Crystal and molecular structure of bis(N-tosylglycinato)tetraaquocobalt(II) and bis(N-tosyl-β-alaninato)tetraaquozinc(II) complexes

The interactions between N-tosylamino acids and cobalt(II), nickel(II) and zinc(II) ions in aqueous solution and in the solid state have been investigated. From concentrated aqueous solutions, compounds of general formula [M(II)(N-tosylaminoacidato)₂(H₂O)₄](M = Co(II), Ni(II) and N-tosylaminoacidato = N-tosylglycinate (Tsgly^?), N-tosyl-α- and -β-alaninate (Ts-α- and Ts-β-ala^?); M = Zn(II) and N-tosylaminoacidate = Tsgly^?, Ts-β-ala^?) and [Zn(II)(N- tosylaminoacidato)₂(H₂O)₂] were isolated and characterized by means of thermogravimetric, electronic and infrared spectra. For two of them: [Co(Tsgly)₂(H₂O)₄](I) and [Zn(Ts-β-ala)₂(H₂O)₄](II) the crystal and molecular structures were also determined. Both compounds crystallize in the monoclinic space group P2₁/c, with two formula units in a cell of dimensions: a = 13.007(6), b = 5.036(2), c = 18.925(7) Å, β = 102.33(3)° for (I) and a = 14.173(6), b = 5.469(2), c = 17.701(7) Å, β = 106.63(3)° for (II). The structures were solved by the heavy-atom method and refined by least-squares calculations to R = 0.031 and 0.064 for (I) and (II) respectively. The cobalt and zinc atoms lie in the centers of symmetry, each bonded to two amino- acid molecules through a carboxylic oxygen atom and four water molecules in a slightly tetragonally distorted octahedral geometry. The second carboxylic oxygen atom is not involved in metal coordination. Electronic and X ray-powder spectra suggest that the tetrahydrate complexes of Co²⁺, Ni²⁺ and Zn²⁺ ions of the same amino acids are isomorphous and isostructural. No coordinative interactions between ligand and metal ions were found in aqueous solution on varying the pH values before hydroxide precipitation.     

Synthesis and crystal and molecular structure of a methyl N,N-diethylcarbamylmethylenephosphonato dysprosium thiocyanate complex

Bis-Methyl N,N-diethylcarbamylmethylenephosphonato dysprosium thiocyanate, Dy[O₂P(OCH₃)CH₂C(O)N(C₂H₅)₂]₂(NCS) was prepared from the combination of ethanolic solutions of Dy(NCS)₃·xH₂O and (CH₃O)₂P(O)CH₂C(O)N(C₂H₅)₂. The complex was characterized by infrared and NMR spectroscopy, and single crystal X-ray diffraction methods. The crystal structure was determined at 25 °C from 3727 independent reflections by using a standard automated diffractometer. The complex was found to crystallize in the monoclinic space group P2₁/c with a = 13.282(4) Å, b = 19.168(5) Å, c = 9.648(2) Å, β = 90.09(2)°, Z = 4, V = 2456.4 ų and ?_cald = 1.72 g cm^?3. The structure was solved by standard heavy atom techniques, and blocked least-squares refinement converged with R_f = 4.7% and R_wF = 4.9%. The Dy atom is seven coordinate and bonded in a bidentate fashion to two anionic phosphonate ligands [O₂P(OCH₃)CH₂C(O)N(C₂H₅)₂^?] through the carbonyl oxygen atoms and one of two phosphonate oxygen atoms. In addition, each Dy atom is coordinated to two phosphonate oxygen atoms from two neighboring complexes and to the nitrogen atom of a thiocyanate ion. This coordination scheme gives rise to a two-dimensional polymeric structure. Some important bond distances include DyNCS 2.433(8) Å, DyO(carbonyl)_avg 2.39(2) Å, DyO(equat. phosphoryl)_avg 2.303(8) Å, DyO(axial phosphoryl)_avg 2.25(2), PO(phosphoryl)_avg 1.493(3) Å and CO(carbonyl)_avg 1.25(1) Å.     

Preparation,properties and crystal structures of nickel(II) complexes with acyclic schiff bases derived from 2,6-diformyl-4-chlorophenol and 1,5-diamino-3-thiapentane or 3,3′-diamino-N-methyl-dipropylamine

Nickel(II) complexes with the compartmental Schiff bases derived from 2,6-diformyl-4-chlorophenol and 1,5-diamino-3-thiapentane (H₂L¹) or 3,3′-diamino-N-methyl-dipropylamine (H₂L²) were synthesized, and the crystal structures of [Ni(L¹)- (py)₂] and [Ni(L²)(dmf)]·H₂0 were determined by X-ray crystallography.Ni(L¹)(py)₂ is monoclinic, space group C2/c, with a= 18.457(6), b = 11.116(7), c= 16.098(6) Å, and β = 115.79(5)°; D_c = 1.49 g cm⁻³ for Z = 4. The structure was refined to the final R of 6.9%. The molecule has C₂ symmetry. The nickel atom is six-coordinated octahedral. Selected bond lengths are: NiO 2.04(1) Å, NiN (L¹) 2.08(1) Å, NiN(py) 2.17(1) Å.[Ni(L²)(dmf)]·H₂O is monoclinic, space group P2₁/n, with a = 17.329(6), b = 13.322(7), c = 12.476(7) Å and β = 95.43(5)°; D_c = 1.45 g cm⁻³ for Z = 4. The structure was refined to the final R of 5.1%. The nickel atom is bonded in the octahedral geometry to the bianionic pentadentate ligand L² and to one molecule of dimethylformamide. Selected bond lengths are: NiO (charged) 2.063(3) Å (mean value), NiO (neutral) 2.120(3) Å, NiN (planar) 2.050(3) Å (mean value), NiN (tetrahedral) 2.177(3) Å.     

A new hydroxo-bridged thorium(IV) dimer: Preparation and structure of di-μ-hydroxo-bis[aquanitrato(2,6-diacetylpyridinedisemicarbazone)thorium(IV)] nitrate tetrahydrate

The pentadentate ligand 2,6-diacetylpyridinedisemicarbazone, DAPSC, reacts with Th(NO₃)₄ in ethanolwater mixture and a di-μ-hydroxo Th(IV) dimer is formed. The compound [Th₂(OH)₂(DAPSC)₂(NO₃)₂(H₂O)₂](NO₃)₄·4H₂O (I) is monoclinic, space group P2₁/n with a = 10.705(1), b = 19.008(2), c = 11.782(1) Å, β = 107.82(2)°, V = 2282(1) ų and Z = 2. Detailed X-ray structural analysis showed that each thorium atom in the complex is coordinated to one pentadentate DAPSC ligand, which is subjected to a considerable distortion, one bidentate nitrate group, one water ligand and two bridging hydroxo groups. The coordination number is ten and the best presentation of the polyhedron is that of a distorted bicapped square antiprism. The ThTh separation is 4.0181(6) Å and the average ThO(H) bridge is 2.366 Å. The structure was refined using 3185 reflections to an R value of 5.0%.     

Comparative structural studies of the first row early transition metal(III) chloride tetrahydrofuran solvates

Two compounds of empirical formula MCl₃- (THF)₃, M = V and Cr, have been characterized by single crystal X-ray studies. The VCl₃(THF)₃ molecule, which has a mer octahedral stereochemistry, crystallizes in the monoclinic space group P2₁/c with a= 8.847(2),b= 12.861(5),c= 15.134(3) Å, β = 91.94(2)°, V = 1721(1) ų and Z = 4. The V-Ci(1) and V-CI(2) distances have a mean value of 2.330 [3] Å while V-CI(3) = 2.297(2) Å, The VO(1) and VO(2) distances have a mean value of 2.061[8] Å while V-O(3) = 2.102(3) Å cis ClVCl angles average 92.0[5]° and cis OVO angles average 86.2[2]° . The isostmctural complex, CrCl₃(THF)₃, has a crystal structure made up of discrete octahedral mer-CrCl₃(THF)₃ molecules with the following unit cell dimensions (space group P2₁/c): a = 8.715(1), b= 12.786(3), c = 15.122(3) Å, β = 92.15(1)°, V = 1684(1) ų and Z = 4. The CrCl(1) and CrCl(2) distances have a mean value of 2.310131 Å while CrCl(3) = 2.283(2) Å. The CrO(1) and CrO(2) distances have a mean value of 2.0101171 Å while CrO(3) = 2.077(4) Å. cis ClCrCl angles average 90.9[4]° and cis OCrO angles average 86.1 [2]°. The structures of these two octahedral complexes and those previously reported for ScCl₃(THF)₃ and TiCl₃(THF)₃ are compared and certain general trends are discussed.     

Trans-bis(benzo(1,3)-thiazole)bis(N,N-dimethylformamide)bis(N-thiocyanato)-cobalt(II): spectroscopy,thermal analysis and crystal structure

Disolution of Co(bzt)₂(NCS)₂ (bzt = benzo 1,3- thiazole) in dimethyl formamide (dmf) produces Co(bzt)₂(NCS)₂(dmf)₂. The stoichionmetry of the complex has been established by a combination of chemical (C, H, N) and thermal analysis. The comlex has an octahedral structure with pairs of ligands in trans configuration as well as a CoN₄O₂ coordination sphere with CoN distances of 2.185(2) Å (bzt); 2.082(2) Å (NCS) and CoN(dmf) of 2.118(2) Å. The infrared and electronic absorption spectra are consistent with this arrangement.     

Synthesis and spectroscopic properties of CpRuCl(R-DAB(4e)) and CpRuCo(CO)3(R-DAB(6e)). Part XVII. X-ray structure determination of CpRuCo(CO)3(t-Bu-DAB(6e))

CpRuCl(PPh₃)₂ reacted with excess R-DAB in refluxing toluene to give CpRuCl(R-DAB(4e)) (1a: R = i-Pr; 1b: R = t-Bu; 1c: R = neo-Pent; 1d: R =p-Tol). ¹H NMR and ¹³C NMR spectroscopic data indicated that in these complexes the R-DAB ligand is bonded in a chelating 4e coordination mode.Reaction of 1a and 1b with one equivalent of [Co(CO)₄]⁻ afforded CpRuCo(CO)₃(R-DAB(6e)) (2a: R = i-Pr; 2b: R = t-Bu). The structure of 2b was determined by a single crystal X-ray structure determination. Crystals of 2b are monoclinic, space group P2₁/n, with four molecules in a unit cell of dimensions: a = 16.812(4), b = 12.233(3), c = 9.938(3) Å and β = 105.47(3)°. The structure was solved via the heavy atom method and refined to R = 0.060 and R_w = 0.065 for the 3706 observed reflections. The molecule contains a RuCo bond of 2.660(3) Å and a cyclopentadienyl group that is η⁵-coordinated to ruthenium [RuC(cyclopentadienyl) = 2.208(3) Å (mean)]. Two carbonyls are terminally coordinated to cobalt (CoC(1) = 1.746(7) and CoC(2) = 1.715(6) Å) while the third is slightly asymmetrically bridging the RuCo bond (RuC(3) = 2.025(6) and CoC(3) = 1.912(6) Å). The RuC(3)O(3) and CoC(3)O(3) angles are 138.4(5)° and 136.5(5)°, respectively. The t-Bu-DAB ligand is in the bridging 6e coordination mode: σ-N coordinated to Ru (RuN(2) = 2.125(4) Å), μ₂-N′ bridging the RuCo bond and η²-CN coordinated to Co (RuN(1) = 2.113(5), CoN(1) = 1.941(4) and CoC(4) = 2.084(5) Å). The η²-CN′ bonded imine group has a bond length of 1.394(7) Å indicating substantial π-backbonding from Co into the anti-bonding orbital of this CN bond.¹H NMR spectroscopy indicated that 2a and 2b are fluxional on the NMR time scale. The fluxionality of 6e bonded R-DAB ligands is rarely observed and may be explained by the reversible interchange of the σ-N and η²-CN′ coordinated imine parts of the R-DAB ligand.     

Synthesis,characterization and crystal structure of 2-dimethylacetal-4-chloro-6-formylphenol and aquabis(2-dimethylacetal-4-chloro-6-formylphenolato)dioxouranium(VI)

The ligand 2-dimethylacetal-4-chloro-6-formylphenol, H(ALAC), prepared by boiling 2,6-diformyl-4-chlorophenol, H(DIAL), in methanol, was reacted with uranyl acetate to obtain the complex [UO₂(ALAC)₂(H₂O)]. The ligand and the uranyl complex were characterized by X-ray crystallography, infrared, ¹H NMR and electronic spectroscopy. Thermogravimetric and mass spectrometry data are also reported. In acid media H(ALAC) transforms easily into H(DIAL). H(ALAC) is monoclinic, P2₁/n, with a=13.951(5), b=7.902(5), c=9.465(5) Å, β= 91.33(3)°. The structure was refined to R=3.9%, based on 1657 observed reflexions. [UO₂(ALAC)₂(H₂O)] is tetragonal, P4₃2₁2, with a=11.147(5) and c=19.150(4) Å. The structure was refined to R=4.0%, based on 2938 observed reflexions. Four ligand oxygens and one water molecule are equatorially bonded to the uranyl group in this compound. Uranium and water oxygen lie in special positions on a crystallographic twofold axis so that the two halves of this molecule are symmetrically related. Selected bond distances for [UO₂(ALAC)₂(H₂O)] are: UO (charged) 2.28(2) Å, UO (neutral) 2.45(2) Å, UO (uranyl) 1.77(2) Å, UO (water) 2.44(4) Å.     

Structural and vibrational characteristics of the tetrasulfatodimolybdenum ions with MoMo bond orders of 3.5 and 4.0

The compound K₄[Mo₂(SO₄)₄]Br·4H₂O has been made and its crystal structure determined. Space group P4/mnc; unit cell dimensions, a = 11.903(2), c = 8.021(1) Å, V = 1136(1) ų. The compound is isomorphous with the analogous chloride whose structure has been reported. The MoMo and MoBr distances are 2.169(2) and 2.926(1) Å, respectively and the [Mo₂(SO₄)₄] ³⁻ ions reside on crystallographic special positions with 4/m symmetry. The Raman spectra of both the bromo and chloro compounds have been measured and the MoMo stretching frequency is 370 ± 1.5 cm⁻¹ in each, for the compounds containing the natural isotopic distribution of molybdenum. The chloro compound has been prepared containing the pure isotope ⁹²Mo as well, and the Raman spectra recorded. The v(MoMo) band is shifted by 6.8 ± 0.5 cm⁻¹. The compound K₄[Mo₂(SO₄)₄]·2H₂O has also been prepared with Mo at natural abundance and with the pure isotope ¹⁰⁰Mo, whereby a shift of 8.5 ± 0.5 cm⁻¹ was found. These and other results will be discussed with regard to the similarity of the Raman spectra of the Mo₂(S0₄)₄³⁻ and M0₂(S0₄)₄⁴⁻ species.     

Synthesis,properties and structure of hexaaquo-tris(N,N-dimethylformamide)-lanthanide trifluoromethanesulfonates

The compounds of general formula [Ln(DMF)₃- (H₂O)₆](CF₃SO₃)₃ (Ln = LaEu, Tb, Dy) were synthesized and characterized by microanalysis, conductance measurements, IR absorption (Nd³⁺) and emission (Eu³⁺) spectra. The crystal structure of the neodymium compound was determined by X-ray diffraction techniques. The compound crystallizes in the triclinic system, space group P1, a = 8.589(4), b = 11.222(2), c = 12.271(2) Å, α = 56.83(2), β = 62.13(2), γ = 75.14(2)°, V = 875.2 ų, M = 918.4, Z = 1, D_c = 1.73 g cm⁻³, λ(Mo Kα) = 0.71073 Å, μ = 1.65 mm⁻¹, F(000) = 456, R = 0.056, R_w = 0.057, for 2979 independent reflections with I > 3σ(I). Nd³⁺ is coordinated to the oxygen atoms of six independent water molecules at a mean distance NdO = 2.52(1) Å, and to the oxygen atoms of three independent DMF groups at a mean distance NdO = 2.40(2) Å. The coordination polyhedron is a tricapped trigonal prism of point symmetry C_3v.     

Three coordination modes of the pentadentate ligand 2,6-diacetylpyridinedisemicarbazone

The pentadentate ligand 2,6-diacetylpyridinedisemicarbazone, DAPSC, reacts with Cr(NO₃)₃·9H₂O and forms two kinds of complexes. At pH=3, the ligand is singly-deprotonated and crystals of [Cr- (DAPSCH)(H₂O)₂](NO₃)₂·H₂O (Ia) are obtained. Evaporation of a solution at pH=0, yields crystals of [Cr(DAPSC)(H₂O)₂](NO₃)₃·2H₂O (II) in which the ligand is fully protonated. The reaction of DAPSC with UO₂(O₂CCH₃)₂ in methanol, followed by crystallization of the product from DMSO yields crystals of [UO₂(DAPSC2H)(H₂O)]·2DMSO (III) in which the ligand is fully deprotonated. Compound Ia is monoclinic, space group P2₁/n with a=11.746(1), b=14.752(2), c=11.866(1) Å,β=105.53(2)°, V= 1981(1) ų and Z=4. Compound II is monoclinic, space group, P2₁/n with a=38.000(3), b= 14.939(2), c=8.233(1) Å, β=96.12(2)°, V= 4647(1) Å and Z=8. Compound III is monoclinic, space group P2₁/n with a=18.048(2), b=15.207(2), c=8.842(1) Å,β=97.72(2)°, V=2405(1) ų and Z=4. The structures were refined using 2084, 4169 and 2516 reflections to R values of 4.4%, 7.8% and 4.8% respectively.     

The crystal structure of 2-deoxy-β-d-arabino-hexopyranose at −150°

2-Deoxy-β-d-arabino-hexopyranose, C₆H₁₂O₅, is orthorhombic, P2₁2₁2₁, with cell dimensions at ?150° [20°], a = 6.484(2) [6.510(3)], b = 10.364(2) [10.427(4)], c = 11.134(3) [11.153(5)] Å, V = 748.2 [757.1] ų, Z = 4, D_x = 1.457 [1.440], and D_m = [1.455] g.cm^?3. The intensities of 1269 reflections were measured by using MoKα radiation. The structure was solved by direct methods, and refined by full-matrix least-squares, with anisotropic, thermal parameters for the carbon and oxygen atoms, and isotropic parameters for the hydrogen atoms. The pyranose has the ⁴C₁(d) conformation, with puckering parameters Q = 0.563 Å, θ = 3.9°, and ? = 350.3°. The departure from ideality is very small, and less than that in β-d-glucopyranose, Q = 0.584 Å and θ = 6.9°. The β-glycosidic, CO bond is short, 1.383(4) Å, and the OCOH torsion angle is ?87°, consistent with the anomeric effect. The hydrogen-bonding scheme consists of infinite chains, with side chains terminating at a ring-oxygen atom.     

Intramolecular hydrogen bonding: synthesis and crystal structure of nickel(II) and copper(II) complexes of a tetradentate amine oxime

In the reaction of the tetradentate ligand 3,3′-(1,4- butanediyldiamino) bis (3-methyl-2-butanone)-dioxime (BnAO) with nickel(II) and copper(II), the monomeric [Ni(BnAO-H)]I·H₂O and a mixed monomer/dimer salt [Cu(BnAO-H)H₂O]₂[(Cu(BnAO-H))₂](ClO₄)₄, respectively, are formed, and all complexes have an intramolecular hydrogen bond between cis oxime groups. The OHO bonds give the characteristic infrared absorptions as well as the downfield proton-NMR signal (Ni complex). [Ni(BnAO-H)]I·H₂O crystallizes in space group P2₁/a with a=13.511(2), b=10.599(2), c=14.096(2) Å, β=97.52°, Z=4 and D_c=1.623 g/cm³. The structure was solved by Patterson and Fourier methods and refined by full-matrix least-squares techniques to a final R of 0.021 for 2124 reflections with I 2σ(I). The nickel(II) atom in the complex has slightly distorted square planar geometry with an intramolecular O···O contact of 2.417(7) Å. The copper(II) complex crystallizes in space group P2₁/c with a =13.425(2), b=21.446(3), c=14.349(4) Å, β= 104.4(5)°, Z=8 (monomers) and D_c=1.485 g/cm³. The final R value for this complex was 0.053 for 3033 reflections with I 2σ(I). This structure contains a monomeric [Cu(BnAO-H)H₂O]⁺ ion and a dimeric [(Cu(BnAO-H))₂]²⁺ ion, having intramolecular O···O hydrogen bonds of 2.421(5) and 2.531(5) Å, respectively. The copper(II) ions have square-pyramidal coordination with the axial positions occupied by an oxygen of the water of hydration in the monomer and by an oxime oxygen atom in the dimer. A center of symmetry relates the two halves of the dimer. The copper atom in each case is out of the plane of the four nitrogen atoms toward the axial site. The copper(II) complex is unusual in that the crystal contains both a monomer and a dimer.     

Metal-phenoxyalkanoic acid interactions. Part 15. The crystal structures of diaquabis(phenoxyacetato)cadmium(II) and catena-μ-[aquabis(phenoxyacetato-O)lead(II)-bis(phenoxyacetato)lead(II)]

The crystal structures of the cadmium(II) and lead(II) complexes of phenoxyacetic acid (PAH) have been determined by single crystal X-ray diffraction techniques. The cadmium complex, [Cd(PA)₂(H₂O)₂] (1), space group C2, with Z = 2 in a cell of dimensions, a = 11.801(2), b = 5.484(1), c = 13.431(3) Å, β = 100.87(2)°, possesses a distorted trapezoidal bipyramidal coordination around the metal atom, involving two water oxygens [2.210(5) Å] and four carboxyl oxygens from two symmetrical bidentate phenoxyacetate ligands [2.363(4), 2.365(4) Å] with Cd lying on the crystallographic two- fold axis. The lead complex, [Pb₂(PA)₄(H₂O)]_n(2) is triclinic, space group P$\text{1}$, Z = 2, with a cell of dimensions, a = 10.135(4), b = 10.675(3), c = 19.285(9) Å, α = 114.66(3), β = 91.94(3) and γ = 114.99(3)°. (2) is a two-dimensional polymer with a repeating dimer sub-unit. The first lead [Pb(1)] has an irregular MO₈ coordination [2.34?2.96(2) Å: mean, 2.63(2) Å] involving the water molecule, two oxygens from an asymmetric bidentate carboxylate group, two from a bidentate chelate [O(ether), O(carboxylate)] group and three from bridging oxygens, one of which also provides a polymer link to another symmetry generated lead. The second lead [Pb(2)] is irregular seven-coordinate [PbO, 2.48?2.73(2) Å: mean, 2.61(2) Å] with three bonds from the bridging groups, two from an unsymmetrical bidentate carboxylate (O, O′) group and one from a second carboxyl group which also bridges two Pb(2) centres in the polymer.     

f-Element/crown ether complexes. 16. Synthesis,crystallization and crystal structure of [Dy(OH2)8]Cl3·18-crown-6·4H2O

When crystals of [Dy(OH₂)₇(OHMe)] [DyCl(OH₂)₂(18- crown-6)]₂Cl₇·2H₂O [1] are allowed to warm from 5 °C to ambient temperature (22 °C) under the original solvent mixture (1:3 CH₃OH: CH₃CN), they redissolve and the title complex can be isolated by slow evaporation of the resulting solution. The crystal structure of this complex, [Dy(OH₂)₈]Cl₃·18-crown-₆·4H₂O, has been determined. It crystallizes in the monoclinic space group, P2₁/c, with a = 10.395(1), b = 18.684(1), c = 16.259- (3) Å, β= 102.56(1)°, and D_calc = 1.61 g cm⁻³ for Z = 4. A final conventional R value of 0.041 was obtained by least-squares refinement using 3453 independent observed [F_o⩾5σ(F_o)] reflections. The [Dy(OH₂)₈]³⁺ cations and crown ether molecules are hydrogen bonded in a polymeric chain with the crown molecules separating the cations and a total of seven DyOH₂···O(crown ether) hydrogen bonds. The chains are connected by a hydrogen bonding network consisting of the cations, chloride ions, and uncoordinated water molecules. The geometry of the cation is best described as a bicapped trigonal prism with distortions on the reaction pathway toward dodecahedral symmetry. The two capping atoms average 2.41(1) Å from Dy, the remaining DyO distances average 2.38(2) Å. The 18-crown-6 molecule has the D_3d conformation normally observed except for a distortion of one OCCO unit containing the oxygen atom accepting two hydrogen bonds.     

Preparation and crystal structure of manganese(II) isothiocyanate tetrahydrate

Crystals of Mn(NCS)₂·4H₂O were isolated from an aqueous solution obtained by mixing solutions of barium thiocyanate and manganese(II) sulphate tetrahydrate. The crystals are monoclinic with a = 7.827(7), b = 9.208(1), c = 7.456(5) Å, β = 112.57(5)°, space group P2₁/c. The structure consists of discrete centrosymmetric trans-[Mn(NCS)₂(H₂O)₄] octahedra linked by hydrogen bonds.     

Coordination chemistry of 7,9-disubstituted 6-oxopurine metal compounds. 4. Platinum(II) coordination at N(1). Molecular and crystal structure of [(ethylenediamine)bis(7,9-dimethylhypoxanthine)platinum(II)] hexafluorophosphate

The preparation and molecular and crystal structure of the complex [(ethylenediamine)bis(7,9,-dimethylhypoxanthine)platinum(II)] hexafluorophosphate, [Pt(C₂H₈N₂)(C₇H₈N₄O)₂] (PF₆)₂, are reported. The complex crystallizes in the monoclinic system, space group C2/c, with a = 12.334(2)Å, b = 10.256(2)Å, c = 22.339(3)Å, β = 101.31(1)°, V = 2771.0ų, Z = 4, D_measd = 2.087(3) g cm^?3, D_calc = 2.094 g cm^?3. Intensities for 3992 symmetry-averaged reflections were collected in the θ-2o scan mode on an automated diffractometer employing graphite-monochromatized MoKα radiation. The structure was solved by standard heavy-atom Patterson and Fourier methods. Full matrix least-squares refinement led to a final R value of 0.051. Both the ethylenediamine chelate and the PF₆^? anion are disordered. The primary coordination sphere about the Pt(II) center is approximately square planar with the bidentate ethylenediamine ligand and the N(1) atoms [Pt(II) ? N(1) = 2.020(5)Å] of two 7,9-dimethylhypoxanthine bases (related by a crystallographic twofold axis of symmetry) occupying the four coordination sites. The exocyclic O(6) carbonyl oxygen atoms of the two 7,9-dimethylhypoxanthine ligands participate in intracomplex hydrogen bonding with the amino groups of the ethylenediamine chelate [N(ethylenediamine) ? O(6) = 2.89( )Å]. The observed Pt ? O(6) intramolecular distances of 3.074(6)Å are similar to those found in other Pt(II) N(1)-bound 6-oxopurine complexes and in several Pt(II) N(3)-bound cytosine systems.     

CoX2(NO)(PMe3)2 Complexes: an example of the influence of X (X = CI,Br, I,NO2) on the stereochemistry and electronic structure of the five-coordinate {CoNO}8 complexes

CoX₂(NO)(PMe₃)₂ complexes (X = Cl, Br, I, NO₂) exhibit markedly different ν(NO) stretching frequencies and different geometries. The structure of CoI₂(NO)(PMe₃)₂ (1) and CoCl₂(NO)(PMe₃)₂ (2) have been determined by X-ray diffraction. Both crystallize in the orthorhombic system, Pnma space group with four molecules in a cell of the following dimensions: for 1, a = 10.497(2), b = 10.694(2), c = 13.975(2) Å, ν= 1568.8, ų; for 2, a = 9.607(2), b = 10.689(2), c = 13.512(3) Å, ν= 1387.5 ų. The structures were refined to conventional R values of R = 0.040 from 1630 reflections for 1 and R = 0.033 from 976 reflections for 2. In both cases, the coordination geometry about the five-coordinate cobalt atom is approximately trigonal bipyramidal, with the NO group sharing the equatorial positions with the halide ligands. Structure 2 is disordered, which prevents any precise structural characterization. In (1), the CoNO angle is 179.2(19)° and the Co NO distance is 1.728(23) Å; v(NO) is 1753 cm⁻¹. CoCl₂(NO)(PMe₃)₃ shows a v(NO) vibration at 1637 cm⁻¹. Co(NO₂)₂(NO)(PMe₃)₂ with v(NO) = 1658 cm⁻¹ has been proposed as a square pyramidal structure with a bent apical CoNO. These differences in NO stretching frequencies and geometries are discussed.